Throughout the world, elsewhere much more than in the United States, people suffer from inadequate nourishment. These inadequacies may involve the total intake, the proteins and amino acids, the vitamins, and the minerals.
Loss of weight is not necessarily an indication of undernutrition nor is maintenance of weight assurance that the intake is proper. Troubles of salt and water balance such as occur in a variety of conditions affecting the heart, kidneys, liver and glandular organs may greatly affect the body weight. Starvation due to loss of appetite or profound neuropsychiatric disturbances produces nutritional disorders. While the human body can build up reserves of some substances, others are used up daily and must be regularly replenished. The effects of undernutrition may be aggravated by excessive action of the thyroid, by heat and by cold.
The regulatory mechanism of the body provides for using up fat to provide energy, before drawing on the vital protein. A gram of fat provides nine calories. A gram of protein or carbohydrate yields four calories. The body conserves its protein, and for that reason a fat person can stand starvation much better than a thin one. The carbohydrate is stored in the liver as glycogen, and this is used up in a day or two of starvation.
Carbohydrate and fat conserve protein. The protein consists of amino acids, of which ten are essential. Twelve other amino acids are classified as nonessential. People on a high carbohydrate diet can develop protein deficiency because they have not had enough protein or because they have not had the essential amino acids in their protein. Eggs, meat, and milk best supply the essential amino acids. Growing children and pregnant women and nursing mothers need excess protein.